Outcome: SGS4.3 Classifies, constructs and determines the properties of triangles and quadrilaterals

 Labelling and naming triangles and quadrilaterals in text and on diagrams The triangle is named Δ ABC The angle at A could be named  BAC,  CAB,  A, BÂC or a ̊ The quadrilateral is named ABCD A B C A B D C

 Using the common conventions to mark equal intervals on diagrams

 Recognising and classifying types of triangles on the basis of their properties Triangles classified by interior angles Acute Right Obtuse (All angles acute) ( 1 right angle) (1 obtuse angle) (0-90 ̊) ( 90 ̊) ( ̊)

Triangles classified by side lengths ScaleneIsoscelesEquilateral (no side equal) ( 2 sides equal) ( 3 sides equal) Base angles equal l ll lll l l l l l x ●○ ●● 60 ̊

 Justifying informally that the interior angle sum of a triangle is 180 ̊.

 The exterior angle equals the sum of the two interior angles opposite angles.     =  +  2 opposite interior  s exterior 

 Using a parallel line construction, to prove that the interior angle sum of a triangle is 180 ̊. As these two lines are parallel, we can use the alternate (or z angle) fact to label the two exterior angles  and  as below. We know that the angle on a straight line on a straight line is 180°, so we can say that  +  +  = 180°. Therefore the interior angles of a triangle add up to 180°.   

 Using a parallel line construction, that any exterior angle sum of a triangle is equal to the sum of the two interior opposite angles.      +  +  exterior  s

 Establishing that the angle sum of a quadrilateral is 360 ̊. 180 ̊

 Let’s start developing the rule ShapeNumber of sides Number of triangles Angle sum triangle311 x 180 ̊ = 180 ̊ quadrilateral422 x 180 ̊ = 360 ̊ pentagon53 _ x 180 ̊ = __ hexagon6_ x 180 ̊ = __ heptagon7_ x 180 ̊ = __ octagon8_ x 180 ̊ = __ n-sided polygon n( __ ) x 180 ̊=